Butadiene polymerization catalyst

ABSTRACT

Process utilizing Ziegler-type catalyst system for polymerizing butadiene to high molecular weight polybutadienes possessing varying proportions of trans-1,4 units, in the range of 50-90 percent comprising: an organoaluminum compound, a Lewis base, and a Ti(halogen)3.nAlI3 composition. The polymers thus obtained exhibit outstanding properties as elastomers when cross-linked and as thermo-elastic polymers in the uncured state.

United States Patent Cozewith et al.

BUTADIENE POLYMERIZATION CATALYST lnventors: Charles Cozewith, Westfield; Erik G. M. Tornqvist, Roselle, both of NJ.

Assignee: Esso Research and Engineering Company, Linden, NJ. Notice: The portion of the term of this patent subsequent to May L6, 1989, has been disclairned. Filed: Aug. 27, 1971 Appl. No.: 175,758

Related US. Application Data Continuation of Ser. No. 788,908, Jan. 3, 1969, Pat. No. 3,642,758.

US. Cl. 252/429 B, 260/943 Int. Cl C08d 1/14 Field of Search 260/943; 252/429 B 45 *Dec. 18, 1973 [56] References Cited UNITED STATES PATENTS 3,47l,46l lO/l969 Tomqvist 252/429 C 3,44l,55l 4/1969 Jezl 252/429 B 3,129,209 4/1964 Hague et al. 252/429 8 3,663,450 5/1972 Cozewith et aL 252/429 B Primary Examiner,Patrick P. Garvin Atrorney,Leon Chasan et al.

[5 7 ABSTRACT 6 Claims, No Drawings 1 BUTADIENE POLYMERIZATION CATALYST CROSS REFERENCE This application is a continuation of U.S. Ser. No. 788,908, filed Jan. 3, 1969, now US. Pat. No. 3,642,758.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a catalyst system and a process for using the same, useful for the stereospecific polymerization of butadiene. More specifically, the catalyst comprises an organoaluminum compound, a Lewis base, and a Ti (halogen) nAlI composition, hereinafter denoted as TiX nAll obtained by fusion or by co-crystalization or intimate mixing as by grinding of the components. This catalyst system is used especially in the production of polybutadienes in which the ratio of trans-1 ,4 to cis-1,4 units can be varied over wide limits and especially within the particularly desirable trans-1,4 range of 50 to 90 percent.

2. Description of the Prior Art Ziegler-type multi/component catalyst systems such as transition metal halides combined with organometallic compounds have been known for well over a decade. The ability of such catalyst to polymerize butadiene to elastomeric products has also been recognized, but the polymers thus produced have generally been characterized by a high cis,-1,4 content rather than trans-1,4 addition units. Thus, for example copending application Ser. No. 408,405, filed Nov. 2, 1964, now US. Pat. No. 3,471,461, discloses the use of TiX 'nAll -xAl(alkyl) catalyst systems for the polymerization of butadiene, in which the steric arrangement of the resulting polybutadiene is predominantly cis-1,4.

Other catalysts, particularly based on vanadium compounds, capable of producing polybutadienes containing more than 90 percent trans-1,4 addition units have also been developed, but the polymers thus produced have been characterized by resinous or plastic rather than elastomeric properties.

The prior art also contains a number of references which disclose that the addition of Lewis bases to certain catalyst systems which normally produce high cisl,4 polybutadienes, causes a decrease in the cis-1,4 units and an increase in the trans-1,4 units in the polymer. However, all of these systems employ titanium tetrahalides rather than trihalides, and the addition of the Lewis base is always accompanied by a drastic decrease in the polymerization rate and the catalyst efficiency.

The inventors have now found surprisingly that the addition of certain Lewis bases to the catalyst system comprised of an Al(alkyl) hereinafter referred to as AIR;, and a TiX 'nAlI composition causes a decrease in the cis-l,4 addition of the butadiene monomer and a corresponding increase in the trans-1,4 addition without the catalyst efficiency being adversely affected to any significant extent. They have also found that the novel catalyst system is capable not only of efficiently producing polybutadienes containing larger proportions of trans-1 ,4 addition units than those catalysts disclosed in the prior art, but also of producing predominantly elastomeric polybutadienes containing 50-90 percent of such units. This is a particularly surprising and significant discovery, since polymers of corresponding over-all compositions which have been prepared in the past with the help of other catalysts or polymerization methods have generally exhibited a considerable amount of crystallinity and plastic character. While the inventors do not wish to be bound by any particular explanation for the difference in physical properties between the 50-90 percent trans-1,4 polybutadienes prepared according to this invention and those of the prior art, it is believed that the much more elastomeric character of the former is the consequence of a more random distribution of the cis-1,4 and trans- 1,4 units in the polymer molecules than in the polymers heretofore known.

The purpose of this invention therefore is to describe a new catalyst system for controlling the steric configuration of 1,4 addition units in polymers of conjugated dienes, the process for employing same to produce such dienes and in particular to describe this polybutadiene having predominantly elastomeric properties.

SUMMARY OF THE INVENTION In general, this invention relates to a catalyst system broadly belonging to the Ziegler Group, consisting of a partially reduced salt mixture corresponding to the formula Tix 'nAll where n may represent a value between about 1 and 20, an aluminum trialkyl, and certain Lewis bases. It also relates to the use of said Ziegler type catalysts for the polymerization of conjugated diolefins, butadiene-1,3 in particular, to polymers of attractive and practically valuable properties. While the use of the system comprising TiX -nAlI -xAlR for producing high cis-polybutadienes was described in the previously mentioned US. Pat. No. 3,471,461, it has now been discovered that the modification of said basic catalyst system by the addition of a suitable Lewis base will cause the type of butadiene addition in the polymer to change from predominantly cis-l,4 to trans-1,4, up to about percent of the latter type depending on the level and character of the Lewis base addition. As a general rule, it may be said that the higher the concentration of the Lewis base in the catalyst mixture, the higher will be the trans] ,4 content of the polymer until a certain upper limit has been reached.

The Lewis bases that may be used are heterocyclic thia, aza and oxa compounds, specifically cyclic thio ethers, cyclic ethers, and their derivatives. Such compounds include tetrahydrothiophene, tetrahydrothiopyran, tetrahydrofuran, tetrahydropyran, 2,5-dimethyl tetrahydrofuran, 3-phenyl tetrahydrofuran, 3-ethyl 4- propyl tetrahydrofuran, 2,5-dimethy1 3-chloro tetrahydrofuran, 2-methyl tetrahydrothiophene, 3-phenyl tetrahydrothiophene, 3-ethyl 4-propyl tetrahydrothiophene and 2,5 -dimethyl 3-chloro tetrahydrothiopyran. Particularly preferred among these compounds is tetrahydrothiophene, however, other cyclic thioethers may also be advantageously employed.

The organoaluminum compounds that can be advantageously used for making the catalysts of this invention are trialkylaluminums, such as trimethyaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, triisophenylaluminum, etc. Mixtures of trialkylaluminums and dialkylaluminum halides and alkoxides may also be successfully employed. Among suitable dialkylaluminum compounds to be used in conjunction with trialkylaluminums may be mentioned dialkylaluminum halides, particularly dialkylaluminum iodides, dialkylaluminum alkoxides, etc.

The hydrocarbon diluents used in making the polybutadiene of the present invention should be liquids at the conditions of temperature and pressure used in the polymerization reaction. Suitable diluents include C to C saturated aliphatic or cycloaliphatic hydrocarbons, such as butane, petane, n-heptane, isoctane, n-decane, cyclohexane, methylcyclohexane, etc. and aromatic compounds such as benzene, toluene, xylene, tetraline, isopropyl benzene, etc.

The process of this invention comprises two principal steps. First, the intimate salt mixture comprising TiX and All;,, which may be of a cocrystalline or solid solution character and is preferably prepared by fusion or intense grinding, essentially as described in US. Pat. No. 3,471,461, is added to and dissolved in all or part of the reaction diluent. The final complete catalyst useful for polymerizing butadiene is then prepared by contacting the dissolved salt mixture with the organoaluminum component and the Lewis base, said contacting being preferably carried out in the presence of the diene monomer which may have been added either directly or in solution in another part of the reaction diluent.

While the TiX 'nAll -xAlR and Lewis base may be combined in many different ways to produce an active polymerization catalyst, a particularly preferred embodiment of this invention involves first adding the solid TiX 'nAll component in all or part of the polymerization diluent or solvent, then adding the monomer and finally adding the AlR and the Lewis base. Alternatively, the TiX 'nAll may be added to the polymerization diluent containing the monomer whereupon the AlRg and the Lewis base may be added to form the complete catalyst and start the polymerization. Although the Lewis base may be successfully added before the trialkylaluminum, better results are usually obtained if the Lewis base is added either together with or after the trialkylaluminum, especially when the base is to be employed in the rather large concentrations required for production of polymers containing a predominant amount of trans-1,4 units. In such cases the base seems to interfere with and slow down the reaction between the alkyl-metal and the TiX 'nAll component required for formation of the catalytically active species. By properly utilizing the latter mode of base addition, i.e. by adding the base after the polymerization has been initiated with the unmodified TiX -nAll xAlR catalyst system, it may actually be possible to obtain A-B type block copolymers in which first (A) block has the high cis-1,4 structure characteristic of the polybutadienes made with the unmodified catalyst system and the second (B) has the higher trans- 1,4 structure characteristic of the polybutadienes made with the modified catalyst system. In this instance and in subsequent use, the term modifier refers to the Lewis base. On the other hand, if the Lewis base is added immediately after the AIR;,, the polymerization may be initiated rapidly without any significant amount of rather pure cis-l,4 polybutadiene blocks being formed. Hence, this method is particularly suitable for the production of high trans-1,4 polybutadiene.

The conditions of the polymerization reaction can vary over a wide range. Generally, temperatures ranging from less than C. to about 100C can be used; however, temperatures ranging from 4 to 70C. are preferred. Pressures ranging from subatmospheric to about atmospheres can be employed depending primarily upon the vapor pressure of the diene and diluent in the polymerization reaction. A preferred range would, however, be from atmospheric to about 5 atmospheres. Reaction times ranging from a minute to 250 hours can be utilized depending primarily on the time needed for the desired monomer conversion under the polymerization conditions used; however, it is usually possible to achieve close to the maximum conversion obtainable in 24 hours or less.

The reaction vessel used for the polymerization can be constructed from any material that is inert to the reactants and is capable of withstanding the operating pressures. Reactors made of glass, stainless steel and glass lined steel may thus be employed.

The total amount of catalyst employed in the polymerization of butadiene may vary within rather wide limits depending upon the particular conditions of the polymerization, but is generally in the range of from about 0.001 to about 0.3 wt. preferably 0.01 to 0.1 wt. based upon the total reaction mixture comprising the butadiene monomer to be polymerized and the reaction diluent.

The molar ratio of TiX to A11 employed in preparing the intimate salt mixture can vary within a wide range from about 1:1.0 to about 1:20. The preferred range however for this ratio is from 1:2 to 1:10.

As in the case of the unmodified TiX -nAll xAlR catalyst disclosed in US. Pat. No. 3,471,461, the molar ratio between the trialkylaluminum and the A11 i.e. x/n, is rather critical, although not quite as critical as for the unmodified catalyst, and should be between 5:1 and 1:1, and preferably between 3:1 and 1.4:1. It is believed that the lower sensitivity of the Lewis base modified catalyst system to higher Alli /A11 ratios is the consequence of the inhibiting effect which the Lewis base apparently exerts upon the reaction between the two basic components required for formation of the catalytically active species. Hence, higher AlR /All ratios can be employed especially when the base is added before or simultaneously with the alkylmetal. On the other hand, higher AIR /A11 ratios, above about 5, will eventually lead to deactivation of the catalyst and usually before complete monomer conversion has been accomplished. Such ratios are not particularly recommended, therefore. The optimum ratio, which can be ascertained through text experimentation, also tends to increase with decreasing amounts of A11 in the solid compound, i.e. with decreasing n.

The ratio of Lewis base to titanium in the catalyst mixture controls the steric arrangement of the monomer units in the resulting polybutadiene and, in genera], the greater the concentration of Lewis base employed, the higher the trans-1,4 content in the polymer up to a certain upper limit. The molar ratio of Lewis base to titanium compound may vary from 1:1 to 500:1 depending upon the amount of trans-1,4 structural units desired in the polybutadiene.

Upon completion of the polymerization the catalyst is deactivated by the addition of a small quantity of a suitable deactivating agent, such as a lower alkanol or a solution of an alkoxide of an alkali or alkaline earth metal, e.g. sodium isopropoxide, sodium ethoxide, potassium t-butoxide, etc. The polymer formed may be recovered from the polymerization mixture by standard techniques such as removal of the diluent by steam distillation or by addition of an anti-solvent to precipitate the polymer. The solid polymer obtained is then isolated by filtration, centrifugation, or similar methods.

The molecular weights, expressed as viscosity average m.w., of the butadiene polymers of the present invention range upwards from 100,000 and preferably from 150,000 to 3,000,000. The butadiene polymers contain reactive unsaturation and may be cured to form highly useful vulcanized materials of varying properties. Any one of a wide variety of curing procedures may be employed, such as sulfur curing or free radical curing.

1n the uncured state, the instant buatdiene polymers exhibit tensile strengths of the order of 150 to 2,000 psi., with percent elongation up to about 1,300. The percent permanent set after breaking ranges from about 25 to about 300 percent.

In the cured state, the instant butadiene polymers exhibit tensile strengths of the order of 1,200 to 2,500 psi., with percent elongation up to about 900.

Examples 1-12 A number of butadiene polymerizations were carried out with tetrahydrothiophene (THT) modified Ticl 'nAll xAlEt catalysts inside a nitrogen containing dry box in capped /6 gallon glass jars equipped with magnetic stirrers. THT and AlEt were added together as a mixture of the 1 molar solutions after the solid catalysts component and the monomer had been added to the diluent. The detailed experimental conditions and the results of the polymerizations are reported in Table 1.

The data in Table 1 clearly demonstrate the striking effect of THT addition of the molecular structure (isomer composition) of the polymer and show that polymers containing more than 85 percent trans unsaturation can be obtained in good yields with sufficiently high contents of Lewis base. (See examples 5, 6, 8 and 12).

TABLE I.-EFFECT OF TETRAHYDROTHIOPHENE ON BUTADIENE POLYMERIZATION (100g butadiene-1.3500 cc benzene) Examples 1 2 3 4 5 6 7 8 9 10 ll 12 Catalyst:

TiCln nAlI H Composition, n= 3 3 3 3 3 3 5 5 5 10 10 10 Weight, mg 86 86 86 172 172 344 219 219 439 264 264 264 AlEu, mg.... 38.5 38.5 38.5 77 77 154 103 103 205 143 143 143 ,THT. mg 166 331 441 882 882 265 705 529 331 551 827 AlEt'i/Alh molar ratio 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 2 2 2 THT/TiCl', molar ratio..... 0 30 60 40 80 40 30 80 30 60 100 150 Total reaction time, hrs 19 l9 l9 18 165 163 18 21 18 20 66 67 Results:

Polymer yield, g 89.7 79.5 78.7 78.2 64.7 78.5 90.0 75.0 82.1 84.7 90.0 75.4 Polymer mol. wt. X 10 355 380 440 275 245 295 340 410 115 135 340 510 Polymer unsaturation:

Vinyl, percent 4.7 4.4 3.7 2.9 2.5 2.4 4.5 2.4 3.9 5.4 4.0 2.8 Cis. percent....... 90.6 55.8 30.7 22.4 9.3 10.7 55.6 12.3 34.3 46.4 24.6 9.8 Trans. percent 4.7 39.8 65.6 74.7 88.2 86.9 39.9 85.3 61.8 48.2 71.4 87.4

Corresponds to 9.64 mg= 0.0625 mmole TiCl Complete reaction frequently occurredwithin a ia cried of time b Corresponds to 19.3 mg 0.125 mmole TiCl much shorter than that indicated in the table. Corresponds to 38.6 mg= 0.25 mmole TiCl According to the correlation of Johnson and Wolfangel for c1s Corresponds to 15.4 mg= 0.1 mmole TlCl3. 1.4-polybutadiene, Ind. Eng. Chem. 44, 752 (1952). Corresponds to 30.9 mg 0.2 mmole TlCl:1. 'AlEt and THT were premixed before being added to the reaction mixture.

The polymers of this invention have many varied Examples 13-23 uses. They may be employed in the preparation of tires, The following series of polymerizations were carried inner tubes, hose and tubing, wire and cable coatings, out in dried 8 oz. bottles which were charged under mas well as for a wide variety of coated or molded arti- 45 trogen in the following order: benzene, TiCl -nAlI cles. Those polymers having from 70-90 percent trans benzene-butadiene solution, Lewis base (tetrahydrounsaturation are particularly suitable for the preparathiophene or tetrahydrofuran) and AlEt After the tion of injection-molded articles and possess thermo- AlEt addition, the bottles were capped and the reacelastic properties. 50 tion allowed to proceed at room temperature.

DESCRIPTION OF PREFERRED EMBODIMENTS This invention and its advantages will be better understood by reference to the following examples.

The results of the polymerizations are given in Table 11. These data clearly demonstrate the wide variation in polymer steric structure obtainable with the instant catalyst system when the Lewis base is added prior to the aluminum alkyl.

TABLE II.EFFECT OF LEWIS BASES ON BUTADIENE POLYMERIZATION (15g butadiene'l.3:130 cc benzene, 0.05 mmol TiCl nAll Examples 13 14 l5 16 17 l8 19 20 21 22 23 Catalyst:

TiC1 nAllgt Composition. n 2 2 3 3 3 3 5 5 3 3 3 Weight mg 48.5 98.5 68.8 68.8 68.8 68.8 109.5 109.5 68.8 68.8 68.8 A1Et;|. mg 20.0 20.0 34.2 34.2 34.2 34.2 45.6 45.6 34.2 34.2 34.2 H mg... 85.6 143.0 44.0 132.0 176.0 220.0 184.6 308.0 THF. mg 32.4 34.2 36.0 AlEt /Alh molar ratio 1.75 1.75 2 2 2 2 1.6 1.6 2 2 2 THT orTHF/TiCl molar ratio. 19.5 32.5 10 42 9 9.5 10 Total reaction time. hrs 20 20 20 20 20 20 20 20 0 20 20 TABLE II. Coiltinued (15g butzldiene-l.3:l30 cc benzene. 0.05 mnlol TiCl -nAll l Examples 13 l4 l5 l6 l7 l8 l9 :0 :l :2 13

Results:

Polymer yield, percent 76 72 68 64 6O 52 79 78 9| 48 8 gglymglr l'lllrfslttjvligigolll(') 190 190 I77 H6 [45 I30 los 75 :25 360 345 E inyl, percent... 3.9 3.1 4.7 5.0 4.2 2.8 2.8 2.0 3.9 2.0 2.1

c 2 .3 riiniifiiiem ii 83 Z; la 8? B3 89 3? ii 22 $3 :dded after the Lewis base. "According to the correlation of Johnson and \Volflingcl for cisorresponds to a TH F/(Total Al-Tl) molar ratio of l. l pol yb utadiene. lnd. Chem. 752 (1952i.

Examples 24-27 THT/'liCl molar 50 3 w 0 While most of the catalysts reported in the foregoing Ramon examples will cause very rapid polymerization of the Time, lir. l8 l9 i9 43 butadiene monomer, a delay in the initiation of the po- 53 g; Yield 7] 6 86 7 7g 7 82 8 lymerization reaction is sometimes noticed at the high pomcr Mot I Lewis base levels required for the production of high 205 390 trans unsaturation polymer if the base is added either Unsamauon 2'5 before or together with the trialkylaluminum compo- Cis, PM 1 .3 m nent. That this problem can be largely overcome was L d 19 3 0 I 5 demonstrated in a series of experiments in which the l gfijjgzg j 25:03 mn t ly lia T icli, Lewis base was added immediately (within about 5-10 corres onds to 23.1 mg-().l5 mmole TiCla seconds) after the AlEt 25 "Added immediately after the AlEt,

Since unmodified Ticl -nAll -xAlR catalysts poly- Tablc (g) merize butadiene very rapidly at the concentrations reg Tabllc (h) quired for making polymers in the molecular weight Xamp 7 l d range of about 100-500 x 10 the polymerization will A i butadiene Ymematwns were be initiated almost immediately after the alkylalumi- 30 h THT l T113 3A"3-,.(AlEt3 Catalysts mnum addition. The polymer formed under these condi- Slde gmtrogell comalnmg dry 9 Capped 1k gallon {ions will, of course, be of the g cis l,4 yp glass Jars equipped with magnetic stlrrers. The results ever, as soon as the base is added the character of the reported m Table W again Clearly demonstrate the monomer addition will change in the manner mew strong effect of THT addition on the polymer molecuously disclosed. Hence, if the Lewis base addition is i Structure It Should be noted i that good made shortly after the polymerization has been initiylelds were obtamed.at rather high Alma/AH ranos ated, most of the polymer will be of the type which rewlth T modlfied catalyils (Examples 33 sults when the Lewis base is added simultaneously with and 7 mdlczlmlg h the modified P are less or before the trialkylaluminum This fact is clearly sens tive to variation in the AlR /All ratio than the unbrought out y the data reported in Table In modified ones, at least when the AlR and THT are It should be noted that most of the polymerizations add-ed slmultaneously' Actually It was note-d m the exreported in the table had gone to completion within perimems reporieq m Table as wel-l as m other ex 2-4 hours after the THT addition. This was, for inpenmems slmllar type that an increase m the stance the case in Example 26 where a polymer con- AlRa/Allci from about 2 to a-botilt 3 helpe-d to spged 5 up the initiation of the polymerization reaction, which tainlng 87.2 percent trans unsaturatlon was obtained in tends to be Slowed down by the Lewis base if the latter close to 80 percent yldd' is added before or simultaneously with the AlR It was also noted that the initiation could be speeded up even TABLE III further by employing AlR /All ratios as high as 5. EFFECT OF TETRAHYDROTHIOPHENE ON However, in these cases the polymerization usually BUTADIENE POLYMERIZATION ceased after a certain period of time and well before complete conversion of monomer to polymer had (100g. butadiene-1,3; 500 cc benzene) taken place. Examples 24 25 26 27 It should also be noted that while good polymer Catalyst yields may be obtained at AlR /All ratios up to a value o ri i pl s i t iz 3 3 3 5 of about 5, the amount of trans unsaturation in the W ight. mg l 172" 276" 276 3.29 polymer decreases with increasing AlR /All ratio for E=- g: the same THT/TiX level. Thus, it may also be disad- AlEtalMgla molar vantageous to employ high AlR /All ratios about ratio 1.8 1.8 1.8 1.8 3) from this point of view.

TABLE lV.-EFFECT OF TETRAHYDROTHIOPHENE ON BUTADIENE POLYMERIZATION (100g. butadiene-1.3: 500 cc benzene) Example 28 29 30 31 32 33 34 35 Catalyst:

Tllg 3All mg 207 207 207 207 207 207 207 207 All [13%, mg 7; Z3 Z7 86 I14 I43 214 l 14 mg 3 l 220 220 2:0 661 AlEt lAll molar ratlo 1.8 1.8 1.8 2 2.67 3.33 5 2.67 THT/Til molar ratio. 0 20 30 20 20 20 20 60 'otall reaction time, hrs, 20 21 21 20 19 19 20 140 Polymer yield, g 89.8 93.5 62.0 86.9 88.8 75.1 37.7 92.: golymer mol. wt. t0- 235 160 295 425 310 290 150 460 O ymer Ul'lSfiIUl'flIlOnZ Vinyl, percent.. 5.0 3.7 2.9 4.8 7.0 11.4 11.6 4.7 C15, percent.. 86.1 52.9 32.3 64.2 56.2 64.4 73.1 14.7 Trans, percen 8.9 43.4 64.8 31.0 36.8 24.2 15.3 80.6

Corresponds to 53.6 mg= 0.125 mmole Tilm See Table I. footnote See Table l, footnote fl 7 See Table 11, footnote a 7 Examples 36-38 20 C y a a 0 To demonstrate more generally the usefulness of 1122 22 mg other Lewis bases for modifying TiX -1 1Al1 -xA1R THTP, mg 255.5 383.3

AlEt [All molar ratio 5.4 5.4 5.4 catalysts accord ng to the method of this invention, THTaplTiaamolar ratio 20 30 0 three polymerlzations were carried out wtth Results t t h d thi n THT m Polymer Yield,g 84.9 82.9 87.9 y pyra P as the 9at.alyst Pdlfier Polymer M01. Wt. 10- 300 275 235 The experiments were carried out inside a nitrogen polymer Unsawmion containing dry box in capped 'r gallon glass jars i y 41 equipped with magnetic stirrers. The various compo- L; :3: nents and their amounts used in the polymerizations uconsponds to 19,3 mmole Tick are listed in Table V. The components were charged in "According to the correlation of Johnson and Wolfangel for cis-1,4- the order: benzene, TiCl -3All butadiene, premixed 1 g i Chem" 752 (1952) molar solutions of AlEt and THT P. Xamp es d n The polymerization reaction started almost immedi- Thiee pcilyrgerlzatms were Came g efsemla ately after the addition of the AlEt -THTP mixture as Xamples i i tmSObuty a evidenced by the viscosity increase and the heat generil EF XJ L ,i meta 29 2 5 2 g ation noticeable after only ten minutes. Although the a d a 6 2s THeT ata reportch f a polymerizations had apparently gone to completion cfear y emonstraie t at promotes t e ormanon after about 3 hours as indicated by the viscosity of the o trans'14 butadlene umts m the System reaction mixtures, the experiments were allowed to continue for 3 days at which time the catalyst was deac- TABLE VI tivated by the addition of 30 ml of a 0.2 molar solution EFFECT OF TETRAHYDROTHIOPHENE ON of sodium tsopropylate in isopropanol. After 0.5 g BUTADIENE POLYMERIZATION phenyl-beta-naphthylamine dissolved in 500 ml ben- 4 zene had been added as an antioxidant and thoroughly 39 4) I mixed wlth the polymer, the benzene was evaporated 45 'ric1,,sA11,. mg 109.6" 109.6 109.6 off at room temperature and the polymer dried in lpgl -5 233 vacuo at about C. THT7'I II molar ratio 0 2 5 From the yields and compositions of the polymers re- (i-Bu).(A11, ported in Table V, it is quite clear that the addition of $2131? 2 2 2 THTP to the basic TiX 'nAll -xAlR catalyst system 50 Polymer Yields (Examples 36 and 37 as contrasted with Example 38) :i'glf 86 HO greatly promotes the formation of trans-1,4 units with- Polymer Unsaturation t th Vinyl, 4.0 3.2 3.4 e polymer yield being slgnlficantly affected. Cis, 870 359 278 Trans, 9.0 60.9 67.8 TABLE V "corresponds to 7.71 mg 0.05 mmole TiCl Example 37 Tables VII and VIII hereinbelow set out the physical properties of representative varying cis-trans randomly distributed polybutadiene compositions in their respec- 38 60 tive uncured and cured states:

TABLE VlL-PHYSICAL PROPERTIES OF VARYlNG ClS-TRANS COMPOSlTlON POLY- BUTADIENES (UNCURED) Percent Tensile permanent Percent trans" Vis. avg. strength Percent set after 'I'ested unsuturation M. W. in p.s.i. elongation break at Extenders TABLE VIL-Continued Percent Tensile permanent Percent trans Vis. avg. strength Percent set after Tested unsuturation M. W. in p.s.i. elongation break at Extenders 250.000 590 570 25 250,000 130 I. 37.5 260,000 1720 1000 300 260,000 480 50 260,000 940 760 125 65 parts Flexon. 260,000 690 540 125 65 20 parts Flexon.

20 parts HAF."

" Hnlnncc: cis-l.4 and vinyl.

l-lcxun 846 is u purnffinic petroleum oil having properties corresponding to AS'I'M 4 and used for extending elustoiners.

" HAF is at high abrasion furnace carbon black.

The compounding recipe for the polybutadienes in Table VIII was as follows:

Parts Polybutadiene 75.00 Hcvea Rubber (Smoked shccts) 25.00 Phenyl-B-naphthylaminc 0.50 ZnO 5.00 Stcaric Acid 2.00 Bcnzothiazyl disulfide 1.00 Bismuth Dimethyldithiocarbamatc 0.50 Sulfur 0.35

This material was cured for 60 minutes at 141C.

TABLE VIII Physical Properties of Varying cis-trans Composition Polybutadienes (Cured) trans 1,4 Viscosity Avg. Tensile Tested Unsaturation M. W. Strength Elongaat C.

psi tion 64.8 295,000 1240 460 73.6 295,000 1400 8l0 25 78.2 275,000 1140 800 25 78.3 250000 2000 830 25 80.4 235,000 1450 850 25 83.4 260,000 2060 850 25 Further advantages of this invention will be apparent to those skilled in the art. Polymers of conjugated dienes that are readily sulfur curable can be conveniently and efficiently prepared with the catalyst system of the present invention. It is understood that this invention is not limited to specific examples set forth herein, which have been offered merely as illustration, and that modifications may be made without departure from the spirit and scope of the appended claims.

What is claimed is:

l. A hydrocarbon-soluble catalyst system for the polymerization of conjugated diolefins consisting of:

a. TiX 'nAlI wherein X is a halogen selected from the group consisting of chlorine, bromine and iodine and n is a number from 1 to about 20;

b. an organo aluminum compound selected from the group consisting of l) trialkyl aluminum and (2) a mixture of trialkyl aluminum and dialkyl aluminum halide; where the ratio of organo aluminum to A11 is from 5:1 to 1:1; and

c. a Lewis base, selected from the group consisting of tetrahydrothiophene, tetrahydrofuran, tetrahydrothiopyran, tetrahydropyran and 2,5-dimethyltetrahydrofuran, where the ratio of base to TiX is from 1:1 to 500:1.

2. The catalyst system of claim 1 wherein the 3. The catalyst system of claim 1 wherein the organo aluminum compound is an aluminum trialkyl.

4. The catalyst system of claim 1 wherein the organo aluminum compound is aluminum triethyl.

5. The catalyst system of claim 1 wherein the organo aluminum compound is aluminum triisobutyl.

6. The catalyst system of claim 1 wherein the mole 50 ratio of the organo aluminum to All is between 3:1 and 

2. The catalyst system of claim 1 wherein the TiX3.nAlI3 is TiCl3.nAlI3.
 3. The catalyst system of claim 1 wherein the organo aluminum compound is an aluminum trialkyl.
 4. The catalyst system of claim 1 wherein the organo aluminum compound is aluminum triethyl.
 5. The catalyst system of claim 1 wherein the organo aluminum compound is aluminum triisobutyl.
 6. The catalyst system of claim 1 wherein the mole ratio of the organo aluminum to AlI3 is between 3:1 and 1.4:1. 